The American National Standard for anesthetic equipment, specifies the approved dimensions and configurations for tracheal tubes, including the angle of bevel at the patient, or distal, end, the location of the Murphy eye if used, the location of the balloon, or cuff, and its inflation tube, and the radius of curvature of the tube. Such tubes may be marked oral, nasal, or oral/nasal. Sharp points, or rough edges, on the patient end of the tracheal tube, on the bevel, or on the Murphy eye may cause mucosal damage and conventional stylets are used to provide smooth passage between the vocal cords in the throat.
It has long been known to use a conventional stylets to guide the distal end of a tracheal tube as it is inserted into a patient's mouth and down into the trachea such as disclosed in U.S. Pat. No. 3,659,612 to Shiley of May 2, 1972. The blunt rounded end of the obturator has the same outer diameter as the inner diameter of the bore of the tube, and the tube end is chamfered to produce a smooth surface and avoid gouging or cutting of any tracheal tissue with any sharp edges.
A similar bullet shaped guide is provided at the end of a stylet for inserting the inner end of a tracheal tube with nontraumatic insertion in U.S. Pat. No. 4,351,330 to Scarberry of Sept. 28, 1982.
In the syringe art, U.S. Pat. No. 724,912 to Montgomery of Apr. 7, 1903 discloses a syringe nozzle having an elongated straight hollow stem of hard rubber with a central passage for liquid and a disc at its discharge end formed of soft flexible material which is normally cup shaped, but adapted to fold in either direction to be inserted in, or withdrawn from, an orifice to be treated.
However, the Montgomery patent seeks only to seal against liquid pressure and its cup shaped disc while perhaps adequate to seal the rectum against the escape of liquid under pressure would be too flexible and flimsy to guide the distal end of a tracheal tube while smoothing the passage of the hard, open, distal end thereof.